Estimating the predictive validity of diabetic animal models in rosiglitazone studies.

For therapeutic studies, predictive validity of animal models - arguably the most important feature of animal models in terms of human relevance - can be calculated retrospectively by obtaining data on treatment efficacy from human and animal trials. Using rosiglitazone as a case study, we aim to determine the predictive validity of animal models of diabetes, by analysing which models perform most similarly to humans during rosiglitazone treatment in terms of changes in standard diabetes diagnosis parameters (glycosylated haemoglobin [HbA1c] and fasting glucose levels). A further objective of this paper was to explore the impact of four covariates on the predictive capacity: (i) diabetes induction method; (ii) drug administration route; (iii) sex of animals and (iv) diet during the experiments. Despite the variable consistency of animal species-based models with the human reference for glucose and HbA1c treatment effects, our results show that glucose and HbA1c treatment effects in rats agreed better with the expected values based on human data than in other species. Induction method was also found to be a substantial factor affecting animal model performance. The study concluded that regular reassessment of animal models can help to identify human relevance of each model and adapt research design for actual research goals.

Scientists and the 3Rs: attitudes to animal use in biomedical research and the effect of mandatory training in laboratory animal science.

The 3Rs principle of replacement, reduction, and refinement has increasingly been endorsed by legislators and regulatory bodies as the best approach to tackle the ethical dilemma presented by animal experimentation in which the potential benefits for humans stand against the costs borne by the animals. Even when animal use is tightly regulated and supervised, the individual researcher's responsibility is still decisive in the implementation of the 3Rs. Training in laboratory animal science (LAS) aims to raise researchers' awareness and increase their knowledge, but its effect on scientists' attitudes and practice has not so far been systematically assessed. Participants (n = 206) in eight LAS courses (following the Federation of European Laboratory Animal Science Associations category C recommendations) in Portugal were surveyed in a self-administered questionnaire during the course. Questions were related mainly to the 3Rs and their application, attitudes to animal use and the ethical review of animal experiments. One year later, all the respondents were asked to answer a similar questionnaire (57% response rate) with added self-evaluation questions on the impact of training. Our results suggest that the course is effective in promoting awareness and increasing knowledge of the 3Rs, particularly with regard to refinement. However, participation in the course did not change perceptions on the current and future needs for animal use in research.

The anaesthetic combination of ketamine/midazolam does not alter the acquisition of spatial and motor tasks in adult mice.

The ketamine/midazolam association of a dissociative with a sedative agent is used for the induction and maintenance of anaesthesia in laboratory animals. Anaesthesia may interfere with research results through side-effects on the nervous system, such as memory impairment. It is known that ketamine and midazolam affect cognition; however, their effects have not been clarified when used in a context of balanced anaesthesia. Thus, this study evaluated the effects of ketamine/midazolam on the acquisition of motor and of a spatial memory task in adult mice. Twenty-eight C57BL/6 adult male mice were divided into three groups: untreated control, treated with ketamine/midazolam (75 mg/kg / 10 mg/kg) and treated with midazolam (10 mg/kg) groups. Respiratory rate, heart rate and systolic pressure were measured every 5 min in the animals treated with ketamine/midazolam, as this was the only group that exhibited loss of the righting reflex. One day after treatment, animals were tested in the open field, rotarod and radial arm maze. There were no differences between treatments regarding open-field activity, rotarod performance or number of working and reference memory errors in the radial arm maze task. In conclusion, the learning process of spatial and motor tasks was not disrupted by the anaesthetic combination of ketamine/midazolam. These results suggest its safe use in adult mice in projects where acquisition of a spatial and motor task is necessary.

Influence of strain and parity on the risk of litter loss in laboratory mice.

Pup mortality is a considerable problem in laboratory mouse breeding and the view that parity influence survival of newborn mice is widespread. Some evidence suggests that maternal behaviour is related to offspring mortality in mice. Parental experience is a factor that can improve maternal behaviour and offspring survival in some mammals. However, few papers report a relationship between parity and pup survival in mice. We investigated the influence of strain and parity on loss of entire litters of C57BL/6 and BALB/c mice using data from a breeding colony. In total, 344 C57BL/6 and 146 BALB/c litters were included. We found a considerable mortality rate for both strains: 32% of C57BL/6 litters and 20% for BALB/c litters were lost. There was a significant difference in survival of the first litter between strains, with 3.6 times higher odds of mortality in C57BL/6 mice (p = 0.0028). Parity or previous parental experience of litter loss did, however, not affect litter loss. The scientific literature does not provide a clear picture of perinatal mortality in laboratory mice. Very few studies report perinatal mortality, and only a handful of papers exist where mortality was systematically studied; this area is thus poorly understood. If perinatal mortality in mice is not recognized and investigated, but instead considered normal when breeding mice, a serious welfare problem might be overlooked.

Environmental enrichment does not compromise the immune response in mice chronically infected with Mycobacterium avium.

Research on infectious diseases using animal models has been a successful example of translational research. However, because chronic infections are still one of the main causes of death and disability in the world, it is expected that a great number of mice will continue to be used to address this subject. Although increasing awareness regarding animal welfare has led to novel recommendations for animal housing enrichment, studies evaluating the impact of these modifications on the immune response to infection are lacking. The present study shows that validated and recommended simple environmental enrichment does not interfere with the immune response to chronic infection with Mycobacterium avium for up to 20 weeks, as assessed by the bacterial load in the spleen and lung, by the number and activation status of the main cell populations of the immune system and the serum concentration of interferon-gamma. Therefore, enrichment can be encouraged without concern regarding comparability of results among laboratories studying this type of chronic infections.

Contribution of animal models to the understanding of the metabolic syndrome: a systematic overview.

The metabolic syndrome (MetS) is one of the most important challenges to public health and biomedical research. Animal models of MetS, such as leptin-deficient obese mice, obese spontaneously hypertensive rats, JCR: LA-cp rats and the Ossabaw and Göttingen minipigs, have contributed to our understanding of the pathophysiological basis and the development of novel therapies. For a complex disease syndrome, no animal model can be expected to serve all needs of research. Although each animal model has limitations and strengths, used together in a complementary fashion, they are essential for research on the MetS and for rapid progress in understanding the aetiology and pathogenesis towards a cure. The purpose of this review is to assess how current animal models contributed to our knowledge of the human MetS, and to systematically evaluate the strengths and weaknesses of the currently available 78 animal models from 11 species.

Intraperitoneal anaesthesia with propofol, medetomidine and fentanyl in mice.

Fast recoveries are essential when looking for a safe anaesthetic protocol to use on mice. Propofol is a short-acting anaesthetic agent, which provides a smooth, fast recovery. A recent study carried out in our laboratory showed that the intraperitoneal (i.p.) administration of propofol combined with a fast-acting opioid does not provide a sufficiently stable anaesthesia. In this experiment, we hypothesized that the additional application of medetomidine would increase muscle relaxation and analgesia. Fifty-four male CD1 mice, divided into six groups of five and three groups of eight, were used to test nine different combinations of propofol, medetomidine and fentanyl administered i.p. and reversed with atipamezole 30 min after induction. These combinations were composed in the following manner: propofol 75 mg/kg, medetomidine 1 and 2 mg/kg and fentanyl 0.1, 0.15 and 0.2 mg/kg. The depth of anaesthesia, loss of righting reflex, loss of pedal withdrawal reflex, pulse rate and respiratory rate were recorded along with the duration and quality of the recovery. The combination of propofol and medetomidine provided a predictable induction, hypnosis and muscle relaxation, but surgical anaesthesia (loss of pedal withdrawal reflex) was not achieved. The addition of fentanyl increased analgesia leading to surgical anaesthesia. We concluded that a combination of 75/1/0.2 mg/kg of propofol, medetomidine and fentanyl, respectively, is a safe, easy and reversible technique for i.p. anaesthesia in mice, providing a surgical window of 15 min and restraint for 30 min with a fast recovery.

Intraperitoneal propofol and propofol fentanyl, sufentanil and remifentanil combinations for mouse anaesthesia.

The combination of propofol and a rapid-acting opioid, such as fentanyl, sufentanil or remifentanil, is a relatively safe, total intravenous anaesthesia technique, commonly used in humans and which has been investigated in laboratory animals. The objective of this study was to evaluate these combinations for anaesthesia of mice by the intraperitoneal (i.p.) route. Sixty-seven mice, divided into groups of four, were used to test 28 combinations of propofol alone and propofol with fentanyl, sufentanil or remifentanil administered i.p. The dose ranges of drugs studied were propofol 50-200 mg/kg, fentanyl 0.2-0.4 mg/kg, sufentanil 0.05-0.1 mg/kg and remifentanil 0.2-1.0 mg/kg. The loss of righting reflex (RR) and the loss of pedal withdrawal reflex (PWR) were recorded along with the duration and quality of recovery. The results obtained in these studies were unpredictable. The same dose combinations of propofol and opioids were associated with different responses in different individuals. Higher doses did not induce loss of RR and PWR in all animals and were associated with high mortality rates. An adequate hypnotic level was only observed with higher doses of propofol. The synergistic effect of propofol and the opioids was not sufficient to allow surgical procedures. Animals that reached PWR loss showed tail rigidity, shaking limbs and scratched their heads with their forefeet. Higher opioid doses induced respiratory depression and higher death rates. The inconsistency between and within groups may be associated with the i.p. route. The results reported here show that the i.p. route is not appropriate for mouse anaesthesia using propofol alone or in combination with fentanyl, sufentanil or remifentanil.

The effect of preweaning and postweaning housing on the behaviour of the laboratory mouse (Mus musculus).

Standard housing for laboratory mice severely restricts natural behaviour and the control that the animal has over its environment. Providing the cage with objects is a method that has been used to both increase environmental complexity, promote the performance of natural behaviour and provide greater controllability for the animal. This method of furnishing cages has mostly been studied in adult animals, and little is known about the influence that the preweaning environment has on the behaviour of mice as adults. This study aimed to investigate the effects on mice behaviour of preweaning and postweaning housing environment. In this experiment, 64 pairs of animals of the strain C57BL/6J were used. Half of the animals were born and reared until weaning in standard cages and the other half in cages twice the size of the standard and furnished with nesting material, a cardboard tube, a PVC nest box and a wooden chewblock. After weaning, half the animals in each group were changed to the other type of cage, whereas the other half remained in the same environment; in both cases they were kept in single-sex pairs of littermates. Behaviour during the dark, active period was studied through video recordings. We found no main effects of preweaning environment on behaviour; however, mice moved from furnished to standard cages at weaning showed a decrease in inactive behaviour at four weeks of age. Mice housed after weaning in standard cages spent less time inactive, and more time engaging in activities like feeding and drinking, self-grooming and allogrooming. A sex difference was also found, in that females showed a greater performance of exploratory behaviour as well as a greater prevalence of stereotypies. The use of different objects and locations within the furnished cage was also analysed at both ages. Results show that at eight weeks of age mice spent more time at the top of the cage, and that the use of the nest box (although not for resting) increased between four and eight weeks. Mice were found to use the nest box as a nesting site/sleeping place only at age four weeks, whereas they always used the nesting material for sleeping.